There is known, for example through the U.S. Pat. No. 4,868,128, a method of dispersing a sample of dry powder in a dispersion chamber comprising:                sealed closure of the said dispersion chamber,        the placing of the sample in means of introducing dry powder into the dispersion chamber,        putting the chamber under negative pressure with respect to a surrounding environment,        dispersion of the dry powder in the chamber by suction thereof inside.        
In addition, the device described in the above mentioned patent comprises:                a dispersion chamber connected to a negative-pressure source and situated in a surrounding environment,        means of opening and/or sealed closure of the said dispersion chamber, and        means of introducing the sample of dry powder into the said dispersion chamber.        
Unfortunately, this method and this device cause an ordered dispersion of the grains constituting the dry powder because of the existence of a flow and this involves segregation within the dispersed granular materials, preventing a certain homogeneity of dispersion of the grains on a surface.